Stannous fluoride has been shown to be effective in combating tooth decay. While various mechanisms have been proposed to explain the action of this anti-cavity agent, there has been a surprisingly small amount of published literature concerned with the actual products of the reaction between stannous fluoride and dental enamel. Building on what work has been done in the past, it is the objective of this research project to study the reaction and structural chemistry of the products formed when dental enamel is treated with stannous fluoride. The structural studies will be carried out by means of single crystal X-ray diffraction techniques. An attempt will be made to relate the structures thus determined to the structure of the principle crystalline component of dental enamel, hydroxyapatite. The chemical studies will consist of isolating the products in pure form, and characterizing them in terms of their chemical and physical properties such as solubility, reactivity toward acids and bases, etc. An attempt will be made to understand why these compounds form rather than other possible products of the stannous fluoride-hydroxyapatite system. Thus this line of research might include broadening the scope of the project to include the study of some compounds which are not necessarily the direct products of a reaction between stannous fluoride and dental enamel.